The present invention relates to a method and apparatus for detecting a rotation angle, and more particularly to an angle detection method and apparatus for outputting an absolute value signal representing a measured rotation angle.
An angle detection method and apparatus for outputting an absolute value signal representing measured rotation angle have been disclosed in JP-A-58-47212.
In the disclosed angle detection method and apparatus, patterns of a plurality of channels are formed with a slight rotation angle deviation from each other so that a combination of patterns of the respective channels corresponds to a predetermined angle, and the angle is detected as a specific binary coded signal. Where a fine signal is required, a parallelly arranged increment type detector is activated to detect a fine angle.
In the above prior art technique, if there are five channels, 2.sup.5 =32 combinations of patterns are possible. Accordingly, an angular measurement range (360 degrees in the prior art technique) is divided into 32 sections such that a first section has 360/32 degrees, a second section has 360/32 degrees x 2, a third section has 360/32 degrees .times.3, ----- , an n-th section has 360/31 degrees .times.n (where n is an integer between 1 and 32). In this manner, specific angles are allotted to 32 binary codes and the angles may be detected as 32 absolute values.
In this arrangement, however, if an absolute signal for every one degree is needed, 360 combinations of patterns are required. To this end, at least ten channels are required, and hence a large scale of sensors are required.
When a fine angle signal is produced by activating the parallelly arranged increment type detector, an absolute value signal is not produced.